1. Field of the Invention
This invention relates to vehicle suspension systems for wheeled vehicles and, more particularly, to a split-beam suspension system suitable for a wide variety of applications from standardized parts and wherein an air spring is positioned on the axis of the frame and the axis of one end of the split beam.
2. Description of Related Art
Vehicle suspension systems having trailing arms suspended from a vehicle frame and a wheel bearing axle suspended from the arm with an air spring mounted between the frame and the trailing arm of the suspension system are disclosed in U.S. Pat. No. 4,693,486 to Pierce et al. issued Sep. 15, 1987; U.S. Pat. No. 3,547,215 to Bird issued Dec. 15, 1970; U.S. Pat. No. 4,262,929 to Pierce issued Aug. 21, 1981, and U.S. Pat. No. 4,858,949 to Wallace et al. issued Aug. 22, 1989. In each of these suspension systems, a unitary trailing arm is pivotably attached at one end to the vehicle frame and has an air spring mounted at the other end of the trailing arm between the arm and the frame.
A problem which plagues the manufacturing of such trailing arms is the lack of any standardization or uniformity for trailing arms. Different vehicles require different spacing between the trailing arm or the axle and the underside of the frame. In order to accommodate these differing requirements, manufacturers must develop tooling for each suspension system. In addition, tooling must be created for both the right and the left hand trailing arms because the arms are not interchangeable from one side of the suspension system to the other. Developing tooling for each of these different vehicles and for the right and left hand trailing arms is extremely expensive. Further, offset loads cause a moment to be induced in the beam along a longitudinal axis. For example, as seen in U.S. Pat. No. 4,858,949 to Wallace, the load bearing points of the trailing arm, i.e. the mount at the front end of the arm, the point where the axle is mounted to the arm, and the rear end of the arm upon which the air spring is mounted, do not lie in the same vertical plane or along the same axis. Therefore, a moment is exerted on the trailing arm. These moments have been compensated for by strengthening the trailing arms and the means for mounting the arm to the vehicle suspension as well as adding a substantial transverse beam to direct the loads to the centerline of the beam. This additional structure results in an increase in the overall weight of the suspension system.